Charles l



0. L. BUGKINGHAM.

DUPLEX TELEGRAPH.

Patented May 23, 1882.

' y INVENTOB oooo WITNESSES:

UNITED STATES PATENT Grates.

CHARLES L. BUOKINGHAM, OF ELIZABETH, NE W J ERSEY ASSIGNOIR TO THE WVESTERN UNION TELEGRAPH COMPANY, OF NEW YORK, N. Y.

DUPLEX TELEGRAPH.

SPECIFICATIGN forming part of Letters Patent No. 258,367, dated May 23, 1882.

A Application filed February 11,1882. (NomodeL) To all irhom it may concern Be itknown that I, GHARLEs L. BUCKING- HAM, of Elizabeth, county of Union, and State of New Jersey, have invented a new and useful Improvement in Telegraphy, of which the following is a description, reference being had to the accompanying drawing, forming a parthereof.

, My invention is applicable to differential systems of telegraphy for the simultaneous transmission of messages upon a single line in opposite directions, and has for its special object the neutralization in the receivin ginstruments of duplex, quadruplex, or sextuplex telegraphy 'ofdisturbingefi'ects due tostatic induction upon.

current will flow through the two oppositely wound coils of the home receiving-relay both while the mainline is receiving its inductive charge and thereafter, during the continuance of a signal and after the main line has received its full inductive charge.

It' is well understood in the art of duplex telegraphy thatin a differential duplex while the mainline is receiving its inductive charge a stronger current will flow through the mainline coil 'than through the oppositely-wound coil in the artificial circuit, and that the differential receiving-relay will respond to give a false signal. The bridge, however, which I employ effects a complete balance of currents sent through them froni the home station. Following each signal that is sent from the home station is a quick static or inductive discharge from the main line in a direction opposite to that of the current of charge. The Carrent of inductive discharge being similar to a signal-current from a distant station, though shorterin duration, will tend to cause the bridge to be broken. However, the armature of the bridgeis so adjusted that the bridge will practicall y remain unbroken from the effects ofsaid inductive discharge, and it will distribute it self in passing to earth equally throughthe two oppositely-wound coils of the receivingrelay, and no false signal will follow. While the bridge will not be broken by a quick inductive discharge from the main line, a batterycurrent sent from a distant station suffi- 6o ciently prolonged to produce a signal at the home station will cause the bridge to be opened and remain open during the signal, wherefore the current will only pass through one coil of the home receiving-relay, and a signal will be given. By this means the mainline inductive charge and discharge respectively produce neutral effects upon the receivin g-instrunients wh ensignals are sentfrom the same stations, and this end is accomplished without thenecessity of adjustmentto change the electro-static capacity of an artificial line to balance the highlywariable inductive condition of the main line.

I will now explain ,my invention by reference to the accompanying drawing.

The drawing represents an ordinary duplex system in which the bridge at each station is broken by means of an ordinary differential electromagnet whose coils are in the main and artificial lines, respectively.

A and B represent two distant stations joined bya main line, L.

M and M are two main-line batteries, ar-

ranged to oppose each other when simultaneously connected to line. In all other respects the devices of station B are identical with those of station A, and a description of apparatus of one station will suffice for that of both.

R is an ordinary differential receiving-relay, go I having oppositely-wound coils m and 3 forming parts respectively of the main and artifi cial circuits, and c is its armature-tongue.

V K is an ordinary transmitter-key, though'in practice a continuity-preserving one is prefer- 5 able,

T is a resistance placed in the artificial circuit equal in amount to the maindine resistance The artificial line is' connected to earth atE zoo S is a differential eleetro-ma-gnet altogether similar in general respects to relay It, its coils z and to being oppositely wound and forming parts of the main and artificial lines.

2and 3 are points in the main and artificial lines, joined with a bridge or branch conductor of very low'resistance, which is usually closed through armature a and stop I).

r is a small rheostat for establishinga proper proportion of resistances between points 1 and 2 and 1 and 3.

When K is depressed the current of battery M divides at point 1, one portion passing through coils w and z and the other'through coils y and w of the relay R andelectro-magnet S. When the two portions of the current thus divided are equal the electromagnetic ef-- fects of wand yare neutral, also those of z and w; but owing to the greater capacity of the main than the artificial line for a static charge the current fromM at the beginning of each signal will, if there be no compensating de-; vice, be stronger through coils a: and z of the main line than through coils y and w of thc{ However, if points 2and be connected by a bridge which is normally f closed, it is obvious that until such bridge is broken the current flowing through coil m mustiequal that passing through 4 ,-evcn if the current which flows to the main line from, point 2 is much greater than that flowing over the artificial line from point 3 to E rily, therefore, owing to the normally-closed artificial circuit.

Primabridgejoining points 2 and 3, the current ofM will be divided equally through the coils wand 3 but while the bridge causes an equal division of current between coils a: andy, more current at the same time will flow through coil 2 than 10, whereby S will become magnetic and tend to attract its armature. However, if S be slightly sluggish and armature a properly adjusted, the bridge will not be broken until the main line will have received its inductive charge. After the line has received its inductive charge the current from M will divide it self at 1 equally, and it will be immaterial if the bridge be momentarily broken.

When the resistance of the bridge compared with that of either or or y is practicallyzero, and resistances of a0 and y are equal, it will be observed that atthe moment of charging the main line, when more current is flowinginto said main line than to the artificial circuit, a

current will be set up in the bridge from 3 tothe receiving-relay. As the static discharge character will attract armature a and retain it during the time of the signal, and the current will thereby pass wholly through coil 00 to effect a signal. If the batteries M M are both simultaneously upon the line and battery M be then removed, the accompanying static discharge will not neutralize itself by passing through both coils ac and y, as the bridges are broken at both stations when both batteries are to line, and as the bridge at station A so remains broken when M is removed. The static discharge under this condition takes place wholly through a); but this will produce no false signal by at= tractin g c, as c is already attracted from the agency of the closed key at the distant station. The static discharge will therefore only conspire to-hold c in its proper position.

This patent is intended'to cover parts of my invention shown but not claimed in the application for Letters Patent filed by me on the 16th day of June, 1881. I disclaim-the method of rendering the receiving relay or relays of a telegraphic system for simultaneous transmission in opposite directions insensible to the effects of inductive charge and discharge of the'main line, consisting in causing both the inductive charge and discharge respectively to be divided before passing through the receiving-instrument to avoid false signals, since that method is claimed in my aforesaid application; nor do I herein claim any part claimed in said application filed June 16, 1881.

What I claim, and desire to secure by Letters Patent, is-- '1. In a telegraph system for simultaneous transmission in opposite directions, the combination, substantially as specified, at each station of the main line, an artificial line, a difi'erential receiving-instrument, a differential electro-magnet whose oppositelyqvound coils are in the main and artificial lines, respectively, and a bridge-conductor joining the main and artificial lines'which is opened and closed by the agency of said differential electro-magnet.

2. In combination with a duplex-telegraph line, an artificial line, a differential receivingrelay,-a normally-closed bridge or branch condoctor, and a differential electromagnetic circuit-breaker whose armature is adjusted to be insensible to the static discharge from the line, but which is actuated by asufficiently-prolonged current from a distant station to make a signal, whereby the static discharge will pass to earth through both coils of the differential receiving relay or instrument, while a prolonged'signal-current sent from a distant station will cause the bridge-conductor to be' broken.

3. The combination, substantially as specified, of a main and artificial line, differential and an automatic circuit-breaker for opening relay R, differential eleetro magnetic circuitand closing said bridge, whereby said bridge breaker S, and a normally-closed bridge which may be closed both at the time of inductive is broken and closed by means of said circuitcharge and discharge of the main line, sub- 5 breaker S. stantiaily as specified.

4. In a telegraph system for simultaneous Executed by me this 7th day of February, transmission in opposite directions, the com- 1882 bination at each station of a main line, an ar- CHARLES L. 'BUGKINGHAM.

tificial or compensating circuit, a receiving Witnesses: 1 1o instrument, a bridge or branch conductor W. B.VANSIZE, for connecting the main and artificial lines, WVLLARNOUX, 

